The bio-chip is formed by sequentially immobilizing a great number of probe molecules with known sequence onto a support with high density by virtue of microfabrication or microelectronic technique. The probe molecules can be DNA, RNA, protein, sugar, etc. By detecting whether the probe is hybridized with the target species in the sample, gene expression characteristics, genetic defects, protein distribution, response characteristics, etc. can be analyzed.
The analytical method based on bio-chip mainly comprises the steps of sample pretreatment, chip preparation, chip hybridization, chip cleaning and drying, chip detection, etc. At present, there are comparatively advanced techniques and supporting instruments for the preparation and detection of bio-chip. For example, for the most popular glass-based bio-chip, a microarrayer can be used for microarray preparation, and detection thereof can also be performed on a corresponding chip scanner. Besides the chip preparation and detection, the chip cleaning and drying in the process of chip hybridization are one of the most important aspects for the bio-chip technique, and how to improve the controllability and accuracy of the hybridization process has become the major direction and hotspot for the bio-chip technique.
For traditional chip hybridization, a static hybridization method is generally employed with the temperature controlled by air bath or water bath. In such a method, since the hybridization reaction between the target molecules in the hybridization sample and the probe molecules on the chip surface only depends on molecular diffusion mechanism, it tends to require relatively long reaction duration and has low hybridization efficiency, and furthermore, readily results in homogenous hybridization over the whole chip, which is not favorable for quantitative analysis. Besides, after the completion of the hybridization, special cleaning and drying instruments or devices are additionally required for the cleaning and drying of the chip, which is quite complicated. In order to overcome disadvantages of the static hybridization, some dynamic hybridization methods and devices have already been proposed based on vibration mixing, continuous flow or reciprocating flow. For example, a dynamic hybridization method, in which a peristaltic pump is employed to force the hybridization sample to flow circularly over the surface of the microarray, has been proposed by Lee et al., by which method the hybridization duration is reduced from 6 hours of the static hybridization to 2 hours (See, H. H. Lee, J. Smoot, Z. McMurray, D. A. Stahl, P. Yager, Lab Chip, 2006, 6, 1163-1170).
Based on similar principle of circulation flow hybridization, an American company Affymetrix (U.S. Pat. No. 6,391,623) has developed an automatic hybridization system. Although integration of hybridization, cleaning and drying can be realized in such a system, large volume of sample are required in one hand, and on the other hand, interior contamination of pump will be easily resulted, due to the use of peristaltic pump and circulating fluid channel. Furthermore, the slot on the device is only available for the chip purchased from Affymetrix, that is the device is not compatible and versatile. Pneumatic-activated microvalve in PDMS (polydimethyl siloxane) microfluidic chip is utilized by Quake's group to achieve reciprocating movement of the hybridization sample solution in the hybridization chamber, and thereby the reaction rate and hybridization signal are significantly enhanced. (J. Liu, B. A. Williams, R. M. Gwirtz, B. J. Wold, S. Quake, Angew. Chem. Int. Ed. 2006, 45, 3618-3623).
By applying similar principle, reciprocating flow hybridization is realized by the NimbleGen Mixers hybridization instrument developed by Roche NimebleGen employing bubbles generated by a pneumatic valve, through which the detection sensitivity is enhanced by 3 folds, and the hybridization duration is reduced. However, the instrument only has the function for hybridization reaction, and special equipments are respectively required for the chip cleaning and drying, so that the hybridization, cleaning and drying can not be integrated.
Based on the description above, the present biological chip hybridization system has disadvantages such as long hybridization duration and low efficiency, or complicated operational procedure and low integration and automation level.